Ke Xu a, Haofei Huang a, Qunfang Wang a, Ke Tang a b c, Longhui Lin a, Keke Ding a, Meng Cao a b c, Linjun Wang a b c, Jian Huang a b c
a School of Materials Science and Engineering, Shanghai University, Shanghai, 200444, China
b Zhejiang Institute of Advanced Materials, SHU, Jiashan, 314113, China
c Shanghai Collaborative Innovation Center of Intelligent Sensing Chip Technology, Shanghai, 201800, China
## Abstract
In recent years, CdZnTe has attracted extensive attention due to its excellent properties. In this paper, CdZnTe thick films were prepared by close-spaced sublimation (CSS) method. An innovative method of introducing a seed layer is employed to enhance the performance of CdZnTe thick films and their devices. The effect of the seed layer on the properties of CdZnTe thick films was systematically analyzed. The results indicate that the seed layer significantly promotes the uniform distribution and preferred orientation of grains, thereby improving the crystalline quality of CdZnTe thick films. Additionally, the seed layer also enhances the performance of CdZnTe thick film ultraviolet photodetectors. The seed layer is thus a key factor in optimizing the performance of CdZnTe thick films, which is beneficial for promoting its applications in fields such as optoelectronic detection.
## Introduction
CdZnTe is a II-VI direct bandgap compound semiconductor with excellent properties, such as high average atomic numbers, high resistivity, and a large, adjustable bandgap [1]. These attributes enable CdZnTe to have a wide range of applications, including nuclear radiation detection, medical imaging, defense security, solar cells and other fields [[2], [3], [4], [5], [6]]. However, the high growth temperature required for CdZnTe single crystals and the challenges in controlling impurities and defects limit the production of high-quality CdZnTe single crystals [7]. In comparison, the preparation process for CdZnTe thick films is simpler and more conducive to low-cost, large-area production. Therefore, the preparation and application research of CdZnTe thick films have attracted widespread attention [[8], [9], [10]].
The diverse array of techniques employed for the fabrication of CdZnTe thick films encompasses several methods, including close-spaced sublimation (CSS) [11], molecular beam epitaxy (MBE) [12], pulsed laser deposition (PLD) [13], magnetron sputtering method [14] and so on. Each of these methodologies offers unique advantages, while the CSS method stands out for its exceptional characteristics. The CSS method boasts several compelling advantages that make it a preferred choice for the production of CdZnTe thick films. It necessitates relatively simple equipment setups, significantly reducing the complexity and investment costs associated with the process. And it has rapid growth rate and capable of growing high-quality thick films.
But the preparation of CdZnTe thick films by CSS method generally requires a higher substrate temperature, which limits the application of CdZnTe thick films in flexible devices, integrated circuits and other fields. However, at lower temperature environments, the nucleation process of thick films slows significantly, leading to a marked decrease in the nucleation rate. This sluggishness in the initial formation of nuclei leads to a low nucleation density, with sparse distribution of nucleation sites becomes evident. Consequently, the structure of the thick film is adversely impacted, leading to an accumulation of defects such as micro voids, dislocations, and grain boundary irregularities. These defects introduce structural imperfections that can profoundly alter the film's intrinsic properties. Therefore, how to prepare high-quality CdZnTe thick films at lower temperature has become a key research focus.
In many cases, by adding a seed layer, lattice mismatch can be buffered and nucleation density can be increased, which helps to improve the quality of the film [15,16]. In this work, a homogeneous seed layer grown by magnetron sputtering is introduced on the substrate, and then a CdZnTe thick film is prepared on the seed layer by CSS method. By introducing a seed layer, the crystalline quality of CdZnTe thick films was improved. The effects of seed layers on the properties of CdZnTe thick films and thick film photodetectors were investigated in detail.
CdZnTe Association (CdZnTe.com)
https://www.cdznte.com/thesis/effect-of-a-seed-layer-on-the-properties-of-cdznte-thick-films-prepared-by-close-spaced-sublimation-method.html